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From: Stefan Richter <stefanr@s5r6.in-berlin.de>
To: Jarod Wilson <jwilson@redhat.com>
Cc: linux1394-devel@lists.sourceforge.net,
	linux-kernel@vger.kernel.org, linux-scsi@vger.kernel.org
Subject: Re: [PATCH 11/9] firewire: fw-sbp2: enforce a retry of __scsi_add_device if bus generation changed
Date: Fri, 08 Feb 2008 20:58:01 +0100	[thread overview]
Message-ID: <47ACB449.3060200@s5r6.in-berlin.de> (raw)
In-Reply-To: <200802081354.23299.jwilson@redhat.com>

(Adding Cc: LSML)

Jarod Wilson wrote:
> On Wednesday 06 February 2008 04:09:47 pm Stefan Richter wrote:
>> take care that __scsi_add_device does not return success
>> even though the SCSI high-level driver probing failed (sd READ_CAPACITY
>> and friends) due to bus reset.  The trick to do so is to use a different
>> error indicator in the command completion as long as __scsi_add_device
>> did not return.

Or so did I guess, and...

>> An actual failure of __scsi_add_device is easy to handle, but an
>> incomplete execution of __scsi_add_device with an sdev returned would
>> remain undetected and leave the SBP-2 target unusable.
>>
>> Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>
>> ---
>>
>> Jarod, does this work like I assume and fixes your setup of two OXFW911
>> based disks?
> 
> Well, it results in the dmesg spew saying "sd 6:0:0:0: [sdc] Result: 
> hostbyte=DID_NO_CONNECT driverbyte=DRIVER_OK,SUGGEST_OK" -- i.e., 
> DID_NO_CONNECT instead of DID_BUS_BUSY, but other than that, no change in 
> behavior, sdc remains unusable just as before.

...my guess was wrong then.

Either I misunderstood the semantics of the various hostbyte codes in
the command completion return (and then these semantics are
insufficient) --- or SCSI mid layer or high-level implements them wrong.

But before we dive into the SCSI stack or implement parellelism of SBP-2
reconnect and SCSI probing in fw-sbp2, there is another simple and in
hindsight obvious trick we can try.  Stay tuned.

Background for LSML:

In case of unrecoverable transport failures during the execution of
__scsi_add_device, I would like to send appropriate error indicators
from the LLD up to SCSI midlayer so that __scsi_add_device ends in
failure (i.e. returns an error pointer rather than a scsi_device pointer).

Sometimes SCSI core decides to let __scsi_add_device fail, sometimes it
takes the scsi_device offline, sometimes it doesn't do either but
pretends to the LLD that __scsi_add_device was an utter success.  Except
that userspace can't do anything with the scsi_device because e.g. READ
CAPACITY couldn't be executed.
-- 
Stefan Richter
-=====-==--- --=- -=---
http://arcgraph.de/sr/

  reply	other threads:[~2008-02-08 19:58 UTC|newest]

Thread overview: 38+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-02-03 22:00 [PATCH 0/9] firewire-sbp2: misc hotplug related patches Stefan Richter
2008-02-03 22:03 ` [PATCH 1/9] firewire: log GUID of new devices Stefan Richter
2008-02-04  8:14   ` Stefan Richter
2008-02-11 16:53   ` Jarod Wilson
2008-02-03 22:04 ` [PATCH 2/9] firewire: fw-sbp2: add INQUIRY delay workaround Stefan Richter
2008-02-11 17:01   ` Jarod Wilson
2008-02-03 22:07 ` [PATCH 3/9] ieee1394: sbp2: " Stefan Richter
2008-02-11 17:03   ` Jarod Wilson
2008-02-03 22:08 ` [PATCH 4/9] firewire: fw-sbp2: wait for completion of fetch agent reset Stefan Richter
2008-02-04  8:11   ` Stefan Richter
2008-02-03 22:09 ` [PATCH 5/9] firewire: fw-sbp2: log bus_id at management request failures Stefan Richter
2008-02-11 17:16   ` Jarod Wilson
2008-02-03 22:10 ` [PATCH 6/9] firewire: fw-sbp2: don't add scsi_device twice Stefan Richter
2008-02-11 17:19   ` Jarod Wilson
2008-02-11 19:42     ` Stefan Richter
2008-02-12  8:55       ` Stefan Richter
2008-02-03 22:11 ` [PATCH 7/9] firewire: fw-sbp2: logout and login after failed reconnect Stefan Richter
2008-02-11 17:32   ` Jarod Wilson
2008-02-03 22:12 ` [PATCH 8/9] firewire: fw-sbp2: sort includes Stefan Richter
2008-02-03 22:13 ` [PATCH 9/9] firewire: fw-sbp2: fix I/O errors during reconnect Stefan Richter
2008-02-11 18:09   ` Jarod Wilson
2008-02-11 20:21     ` Stefan Richter
2008-02-12  5:07       ` Jarod Wilson
2008-02-12  8:01         ` Stefan Richter
2008-02-16 15:37       ` Stefan Richter
2008-02-16 15:51         ` Stefan Richter
2008-02-04 15:54 ` [PATCH 0/9] firewire-sbp2: misc hotplug related patches John Stoffel
2008-02-04 17:48   ` Stefan Richter
2008-02-04 18:51     ` John Stoffel
2008-02-06  5:17 ` Jarod Wilson
2008-02-06 18:27   ` Stefan Richter
2008-02-06 21:09     ` [PATCH 11/9] firewire: fw-sbp2: enforce a retry of __scsi_add_device if bus generation changed Stefan Richter
2008-02-08 18:54       ` Jarod Wilson
2008-02-08 19:58         ` Stefan Richter [this message]
2008-02-08 21:33           ` [PATCH 11/9 update] " Stefan Richter
2008-02-10 18:36             ` Jarod Wilson
2008-02-16 15:01               ` Stefan Richter
2008-02-06 21:07 ` [PATCH 10/9] firewire: fw-sbp2: preemptively block sdev Stefan Richter

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